Wormery: Earthworm compost

Wormeries provide high quality compost that can be added directly to the garden, by decomposing kitchen left-overs. To start a wormery you require stacked containers (3-4 levels) and some earthworms. Most wormeries commercially available are expensive given the amount of space you get from it.

Wormery Construction

We acquired some meat-slab/solid-crate trays from the plastic shop. You drill some holes in the bottom of two of the trays. The trays with holes are stacked on the third with no holes. This allows the earthworms to move between the first and second trays (through the holes) that contain kitchen waste. The third tray collects any liquid that drips from the top trays, which acts as a good liquid fertiliser.

Wormery Construction

I separate the 2nd and 3rd levels with netting or garden frost fleece to prevent the worms from falling into and drowning in the liquid fertiliser (you do not want to lose your workers ). I did not make additional holes in the side of the containers as I do not want flies and other critters getting in there – so mine is a sealed unit and produces liquid fertiliser every three weeks (in summer) without adding additional water to the wormery.

The earthworms can be purchased from garden store or worm-farm enthusiasts. These are earthworms that are the most efficient at reducing kitchen waste to compost (not your average backyard garden earthworm). I have Tiger earthworms (striped bodies). The earthworms can convert large pieces of kitchen waste, but there are smaller animals that accompany the earthworms and these assist in the decomposition.

Kitchen Waste

Kitchen waste is added to the 2nd layer, until it is full, thereafter food is added to the 1st. Once most of the worms have moved to the 1st layer, the 2nd can be emptied of compost and its worms returned to the wormery. The 2nd tray is replaced with the 1st. (1st and 2nd exchange places so that the empty one is at the top).

Wormery Function

The wormery takes a long time to produce enough compost to add to your garden and the worms take up to one season to establish themselves in terms of the ration of worms:food. All other books and wormery articles suggest not overfeeding the worms (sprinkle food on top of the wormery and do not add more until this is consumed). I do not follow this. I add a thick 5-10 cm layer of kitchen waste that cover the entire surface of the wormery and top it up as soon as the previous layer is black and almost unrecognisable. I have not killed off any worms by over-heating due to over-feeding and have maximised compost output. I think it depends on ‘how to know when to cheat’ . Also, the wormery is located in a weather-sheltered, permanently shaded area. It gets a little morning sun in winter (about 2 hours), but that is it. The following kitchen waste can be added to the wormery (basically the same food one adds to the compost).

DIY Earthworm farm with plastic trays (25 L)

Any plant based material: Tea bags, spent coffee, leaves/stems/roots of vegetables and herbs, flowers and rotten fruits/vegetables, eggshells (to regulate the pH in the wormery, and whole eggshells are nice hide-outs for the worms), peels and shavings of fruits and vegetables (not too much citrus or onions/garlic– rather put those directly in the garden soil/compost). Just about anything, but no meat/gravy/dairy/bread or pasta.

Now some foods the worms really enjoy – they will make a worm mass around the food – peppers, any squishy rotten whole fruit, watermelon leftovers (the flesh especially), tea bags, fresh herb leaves (from pruning the herbs).

The worms I believe become spoiled after some time, only eating soft fleshy waste. Luckily the worms have little crustaceans, detritus beetles and spring-tails that live with them, and these make short work of any tougher foods that the worms don’t really want to eat, such as watermelon rinds, roots vegetable peels, potato peels… These critters will also consume dairy or meat products, which you are not supposed to add to the wormery, but again it is knowing when to cheat. Sometimes we make too much salad and the salad contains only really small feta cheese crumbs – that can be added to the wormery and the crustaceans will have a party . As long as it doesn’t exceed about a matchbox size of cheese/meat for the entire wormery, it should be fine.

Crustaceans feeding on a teabag

A tip for moving around any stray earthworms or returning earthworms that have fallen out of the unit – use a fork to scoop them up in one of the ‘teeth’, it does not harm them, as fingers can’t get a good grip on their wriggly bodies. I also use the fork to scratch around in the pre-soil to check on the worms and the state of the wormery – it does not skewer them and aerates the soil as well. I do not add any grass cuttings or twigs, cardboard or paper to my wormery, as it makes a gloopy mess. I also ‘turn’ the wormery once in a while (once a month, only in summer, leave them be in winter). Put some plastic or non-sterile surgical gloves on, dig your fingers in and mix the pre-soil around. This loosens the soils structure for worm movement and aerates the soil to prevent any rotting/anaerobic conditions forming in the wormery due to the compacted soil.

Other than that, be patient as this quality compost takes time to develop, but the garden will reward you with food like no other compost/fertiliser can. Check Composting (including Instant Compost), Comfrey (coming soon!) and Green Manures (coming soon!) out for additional ways to improve soil structure and nutrients.